DYNAMICS OF POSTTRAUMATIC BRAIN-SWELLING FOLLOWING A CRYOGENIC INJURYIN RATS

For evaluation of novel therapeutic regimens against brain edema in ex perimental models, it is important to know the temporal profile of ede ma formation. Since development of brain swelling and edema following a cryogenic injury is poorly documented in rats, these parameters have been investigated in this study. 27 Sprague-Dawley rats were used. Th ree rats (controls) were sham-operated. Their brains were removed 15 m in after sham-operation. In all other animals a right parietal cryogen ic lesion was applied in ketamine-xylazine anesthesia. Systemic blood pressure was monitored during the perioperative period. Brains were re moved in defined intervals following cryogenic injury (0.25, 0.5, 1, 3 , 6, 12, 24, and 72 h; n = 3 each). Hemispheres were then separated an d weighed for determination of brain swelling, dryed and weighed again . Cerebral water content was calculated as the difference of hemispher ic wet- and dryweight. Posttraumatic hemispheric swelling reached its maximum (7.9 +/- 0.4%) as early as 12 h post trauma. During the first hour after injury, brain swelling showed a steep, linear increase to 3 .9%, i.e. swelling amounted to 50% of its maximum within one hour. 6 h post trauma swelling was 5.7%. After 12 h brain swelling started to d ecline. 72 h post cryogenic injury, 6.1% hemispheric swelling were fou nd. Development of brain swelling was paralleled by a linear increase in brain water content of the lesioned hemisphere. The maximum of hemi spheric water content was seen 24 h post trauma. In non-lesioned hemis pheres only a marginal transient increase in cerebral water content wa s observed. Thus, in rat models the rapid development of brain swellin g and edema has to be considered when planning therapeutic protocols.